1. Field of the Invention
This invention relates to a digital telephone set which is connected to a digital data exchange through a transmission line.
2. Description of the Prior Art
As well known in the art, the digital telephone set is connected to a digital data exchange through a transmission line. In general, the digital data exchange is able to transmit/receive, through the transmission line, a time division multiplexed signal into which a plurality of digital speech signals are multiplexed in a time division fashion. Such a digital data exchange is, for example, a central office in an Integrated Services Digital Network (ISDN) system according to Recommendation Q.911 of CCITT (International Telegraph and Telephone Consultive Committee). The digital data exchange may be a digital Private Branch Exchange (PBX).
A conventional digital telephone set comprises only one handset which is mounted on a telephone body. The handset is connected to the telephone body through a handset cord. Accordingly, the conventional digital telephone set is used by only one person at a time by using one transmission line.